The IEEE 802.16 Standard has defined a Broadband Wireless Access (BWA)-based Wireless Metropolitan Area Network (WMAN) standard, and different physical layer techniques are defined for different frequency bands with respect to applications mainly in Residential Community, Small Office/Home Office (SOHO), Remote Access, and Small Enterprise (SME) markets.
Media Access Control (MAC) defined in IEEE 802.16 is suitable for harsh subscriber environments. The MAC can cope with an application environment with each channel shared by hundreds or thousands of subscribers, and support different traffic such as continuous and burst traffic. The MAC provides an Asynchronous Transfer Mode (ATM) convergence sub-layer and a packet convergence sub-layer. Through processing by the convergence sub-layers, multiple data units from higher layers are encapsulated into a MAC Protocol Data Unit (PDU) for transmission, thereby implementing protocol transparency for ATM, Internet Protocol (IP), and Ethernet services.
The Worldwide Interoperability Microwave Access (WiMAX) is an organization in worldwide microwave access interoperability industry, and aims at facilitating worldwide popularization and application of the IEEE 802.16 series (IEEE 802.16, IEEE 802.16d, IEEE 802.16e) air interface protocols. The WiMAX mentioned herein refers to a network entity that conforms to the IEEE 802.16 air interface protocols.
As shown in FIG. 1, the WiMAX includes a Mobile Subscriber Station/Subscriber Station (MSS/SS), an Access Service Network (ASN), and a Connectivity Service Network (CSN).
1. ASN—Access Service Network
ASN is defined as a set of network functions that provide wireless access service for a WiMAX MSS/SS. An ASN includes network elements of a BS and an ASN-Gateway (GW), and may be shared by multiple CSNs. The MSS/SS is connected to a BS via an R1 interface, BSs are connected to each other via an R8 interface, a BS is connected to an ASN-GW via an R4 interface, and an ASN-GW is connected to a CSN via an R3 interface.
A BS provides an L2 connection between the BS and an MSS/SS, and functions of wireless resource management, measurement and power control, and air interface data compression and encryption, etc.; An ASN-GW provides proxy function for authentication, authorization, and accounting on an MSS/SS, supports network discovery and selection of an NSP, and provides L3 Relay functions (e.g. IP address assignment) for the MSS/SS; in addition, the ASN-GW can provide optional functions such as intra-ASN switching, MSS/SS paging and location management, tunnel management between the ASN and the CSN and visit location registration.
2. CSN—Connectivity Service Network
A CSN is defined to provide IP connection service for a WiMAX MSS/SS. The CSN mainly provides the functions of IP address assignment for the MSS/SS, Internet access, AAA proxy server or server, subscriber-based authorization control, establishment and management of a tunnel between an ASN and the CSN, accounting on WiMAX subscribers and settlement between operators, establishment and management of a tunnel between CSNs and inter-ASNs switching in the case of a roaming MSS/SS, and various WiMAX services (e.g. location-based services, multimedia multicast and broadcast services, IP Multimedia Subsystem services), etc.
3. MSS/SS—Mobile Subscriber Station
MSS/SS is a (mobile) User Equipment, with which a subscriber accesses the WiMAX network.
During the movement of the MSS/SS from the coverage area of BS1 to the coverage area of BS2, after the MSS/SS accomplishes re-entry to a Target BS/ASN-GW, the communication path between the MSS/SS and the CSN needs to be reestablished, with either of the following two methods:
a first method as shown in FIG. 1, in which a new R4 data path is established between the current Serving ASN-GW for the MSS/SS and the Target ASN-GW; the original communication path is indicated as the black heavy solid line in FIG. 1, while the new communication path is indicated as the black heavy dot and dash line in FIG. 1 and includes the new R4 data path established and the original R3 data path;
a second method as shown in FIG. 2, in which the original R3 data path between the Serving ASN-GW and a CSN is redirected to be between the Target ASN-GW and the CSN; the original communication path is indicated as the black heavy solid line in FIG. 2, while the new communication path is indicated as the black heavy dot and dash line in FIG. 2 and includes the redirected R3 data path only.
According to content of relevant draft standards defined by WiMAX currently with respect to Intra ASN R4, during the relocation of the MSS/SS to the Target ASN-GW, an interface data path for the MSS/SS to access the CSN via the Target ASN-GW is established through the following negotiation steps as shown in FIG. 3 after the MSS/SS accomplishes re-entry to the Target BS and the Target ASN-GW.
1. The Target ASN-GW sends an R4 data path establishment request message (Data Path Establishment REQ) to an Anchor ASN-GW (i.e. the Serving ASN-GW for the MSS/SS before the MSS/SS is switched to the Target ASN-GW).
2. If deciding to establish an R4 data path, the Anchor ASN-GW establishes an R4 data path directly, and returns to the Target ASN-GW an R4 data path establishment response message (Data Path Establishment RES) carrying the information related to the R4 data path establishment; when receiving the R4 data path establishment response message, the Target ASN-GW establishes an R4 data path at the local side, and the MSS/SS accesses the CSN via the R4 interface and the R3 interface;
if deciding to redirect the R3 data path, the Anchor ASN-GW includes a Redirection indication in the Data Path Establishment RES message to be returned, to instruct the Target ASN-GW to redirect the R3 data path.
3. Upon receipt of the returned Data Path Establishment RES message carrying the Redirection indication from the Anchor ASN-GW, the Target ASN-GW returns an acknowledgement (ACK) message to the Anchor ASN-GW.
4. Upon receipt of the acknowledgement message, the Anchor ASN-GW sends to the Target ASN-GW a Relocate REQ message carrying the information related to the R3 data path establishment, where the information includes ID information of the MSS/SS, current service information of the MSS/SS, and path information, etc.
5. Upon receipt of the Relocate REQ message, the Target ASN-GW is triggered to send a Registration REQ message to a Home Agent for Client Mobile Internet Protocol (CMIP)/Proxy Mobile Internet Protocol (PMIP) registration, with the ID information of the MSS/SS, the current service information of the MSS/SS, and the like also carried in the Registration REQ message;
depending on the mobile Internet protocol (the CMIP or the PMIP) currently used by the MSS/SS, the Registration REQ message can be a CMIP registration request or a PMIP registration request, where the CMIP registration message must be initiated by the MSS/SS, while the PMIP registration message must be initiated by a Proxy MIP Client at the network side.
6. The Home Agent returns a Registration RES message to the Target ASN-GW, and redirects the R3 data path from the Anchor ASN-GW to the Target ASN-GW.
7. Upon receipt of the Registration RES message returned from the Home Agent, the Target ASN-GW establishes an R3 data path and return to the Anchor ASN-GW an acknowledgement message (Relocate RES) indicating a successful R3 data path redirection.
Upon receipt of the Relocate RES message, the Anchor ASN-GW performs corresponding processes, such as release of the R3 connection.
The existing method is inflexible. At step 2, for example, if the Anchor ASN-GW chooses to establish an R4 data path, the Target ASN-GW has to simply establish an R4 data path, but is unable to choose to redirect an R3 data path according to actual conditions of the Target ASN-GW itself, such as the available bandwidth of R4 and R3 interfaces, the QoS requirement, and other factors. In addition, the message exchange at steps 2, 3, and 4 of the existing process flow is very complex, resulting in longer switching delay.